The superior colliculus of the cat receives visual input from the retina and the visual cortex and has access to motor systems controlling head and eye position. The object of the proposed research is to develop detailed information about the influence of corticotectal and retinotectal visual inputs on collicular neurons, which project to regions of the nervous system involved in orienting and visually guided behavior. This information is necessary to an understanding of how the colliculus participates in the transformation of a sensory code to a motor code, and how the visual cortex influences such a sensory-motor transformation. Collicular efferent neurons will be identified by antidromic stimulation and their receptive fields analyzed to determine if different classes of collicular cells project to different brain regions. Intracortical microstimulation will be combined with electrical stimulation of the optic tract and natural stimulation of the retina to investigate the interaction of the several visual inputs on such collicular output cells. A final series of experiments will study the influence of tectal efferent neurons and the corticotectal projections on oculomotor neuronal responses to visual stimulation.